Patent term calculation is complicated in the US because there are essentially two different systems and quite a few corner cases. Even with a list of patents, it can be tricky to determine when the patents are all expired. Since I am a computer programmer (and not a lawyer), I created a program to try and automate this. This paper discusses how patent term calculation works, and some results from a combination of hand and automatic term calculation for MP3, MPEG-2 and H.264.

Today, when The Reg asked if VP8 was vulnerable to patent attack, Google product manager Mike Jazayeri indicated this isn't a big concern for the company.

"We have done a pretty through analysis of VP8 and On2 Technologies prior to the acquisition and since then, and we are very confident with the technology and that's why we're open sourcing," he said.

It was only because Google were very confident about the patent coverage of VP8 that they even bought the On2 company in the first place. It should also be pointed out that before Google bought On2, no-one had sued On2 over VP8 patents then, either.

MPEG LA made a call for other parties to submit patents they believe read on VP8

This was a very risky thing to do, given the MPEG LA monopoly over H.264, because any party with an obscure patent that did read on VP8, one somehow missed by Google's patent lawyers' allegedly thorough search, should of course negotiate with Google first. I think MPEG LA are now under anti-trust investigation over this call.